On Sun, 23 Feb 2014, Salvador Rodriguez wrote:
 Thanks for taking the time to answer! has clarified the big question
I had,
 have any recommendations of software which allows to generate a series
 arima model for weekly data? 
There's no problem with estimating an ARIMA model on weekly data in 
gretl, and you can even have a "seasonal" component (though 
estimation may take a while). It's just that there's no standard
way of carrying out seasonal adjustment of weekly series.
Allin Cottrell